In a conventional video/audio system in a vehicle, which includes a plurality of interconnected video/audio units with a video or audio output function, and which enables users to listen to a plurality of sources simultaneously via a plurality of audio output circuits, the plurality of users (for example, they are divided into front seat users and back seat users simply called front seats and back seats from now on) can select sources that they want to hear using control sections placed at the individual seats. In this case, it is a master unit that manages which of the sources selected by the plurality of users should pass through which audio output circuits. In other words, the system is constructed on the assumption that the master unit is always connected (see Relevant Reference 1, for example).
Relevant Reference 1: Japanese patent application laid-open No. 10-93878/1998
The conventional video/audio units with the video/audio output function have the foregoing configuration. Thus, without the master unit (a head unit, for example), the other connected units cannot operate. Accordingly, the system without any supposed master unit has a problem of being unable to connect other audio/video units.
Besides, a system having a plurality of interconnected singly operable video/audio units sometimes use similar accessories such as control sections and display units. In this case, as the number of the connected units increases, the number of the accessories also increases. In addition, since the video/audio units having the singly operable video/audio output function are configured as described above, they have a problem of increasing the number of needless accessories every time the video/audio unit is connected.
The present invention is implemented to solve the foregoing problems. Therefore it is an object of the present invention to provide a simple configuration, low cost video/audio system capable of combining a minimum number of components necessary for the system when a plurality of video/audio output units with the video and audio output functions are connected to operate as a system.